I hope you guys can help me again.

I gather from posts here that RG6 is better than RG59, is that right?

Could the use of of RG59, 33 feet, for at least one tv be responsible
for my bad reception on that tv?

I'm using co-ax for distributing tv from my DVDR to TVs throughout the
house. (The DVDR tunes in the over-the-air digital signal and I have
an RF modulator to change the DVDR output to analog. I did the wiring
to the tvs 25 years ago, and I used left-over and scrap co-ax, so the
co-ax is older than 25 years. Did they have RG-6 25 or 30 years ago?
I didn't pay attention then so I don't know what most of it is, but
the 33 foot piece going to this one tv is RMS Electonics Inc. 59/U.

Everything was fine until the digital conversion, and now this tv that
I watch a lot shows a grainy picture. All the other tvs have great
pictures, and even for this one, when I supply a signal directly from
a set-top digital converter box, only 3 feet of cable, it shows a
perfect picture**.

Do you think replacing the RG59 with RG6 will get me the perfect
picture other sets get? I didn't use home-runs, just splitters and
every two splitters a signal amp, a total of three signal amps, one
with 2 or 4 outputs, and two with 2. Would an additional signal amp
at the start of the RG-59 also give me perfect or at least improved
reception?

**(But the set-top box isn't connected to the main antenna and
doesn't get several stations I watch, nor will it play what is
recorded on the DVDR.)

"mm" wrote in message
...
I hope you guys can help me again.

I gather from posts here that RG6 is better than RG59, is
that right?

Could the use of of RG59, 33 feet, for at least one tv be
responsible
for my bad reception on that tv?

I'm using co-ax for distributing tv from my DVDR to TVs
throughout the
house. (The DVDR tunes in the over-the-air digital signal
and I have
an RF modulator to change the DVDR output to analog. I
did the wiring
to the tvs 25 years ago, and I used left-over and scrap
co-ax, so the
co-ax is older than 25 years. Did they have RG-6 25 or 30
years ago?
I didn't pay attention then so I don't know what most of
it is, but
the 33 foot piece going to this one tv is RMS Electonics
Inc. 59/U.

Everything was fine until the digital conversion, and now
this tv that
I watch a lot shows a grainy picture. All the other tvs
have great
pictures, and even for this one, when I supply a signal
directly from
a set-top digital converter box, only 3 feet of cable, it
shows a
perfect picture**.

Do you think replacing the RG59 with RG6 will get me the
perfect
picture other sets get? I didn't use home-runs, just
splitters and
every two splitters a signal amp, a total of three signal
amps, one
with 2 or 4 outputs, and two with 2. Would an additional
signal amp
at the start of the RG-59 also give me perfect or at least
improved
reception?

**(But the set-top box isn't connected to the main antenna
and
doesn't get several stations I watch, nor will it play
what is
recorded on the DVDR.)

Yes RG6 existed 25 years ago. You have something else wrong.
The difference in loss between 33 feet of RG59 vs. RG6 is
negligible at VHF and at most a few dB at the higher UHF
frequencies. What else is in that 33 foot span?

David

On Sat, 5 Dec 2009 15:52:16 -0600, "David"
wrote:



"mm" wrote in message
.. .
I hope you guys can help me again.

I gather from posts here that RG6 is better than RG59, is
that right?

Could the use of of RG59, 33 feet, for at least one tv be
responsible for my bad reception on that tv?

I'm using co-ax for distributing tv from my DVDR to TVs
throughout the
house. (The DVDR tunes in the over-the-air digital signal
and I have
an RF modulator to change the DVDR output to analog. I
did the wiring
to the tvs 25 years ago, and I used left-over and scrap
co-ax, so the
co-ax is older than 25 years. Did they have RG-6 25 or 30
years ago?
I didn't pay attention then so I don't know what most of
it is, but
the 33 foot piece going to this one tv is RMS Electonics
Inc. 59/U.

Everything was fine until the digital conversion, and now
this tv that
I watch a lot shows a grainy picture. All the other tvs
have great
pictures, and even for this one, when I supply a signal
directly from
a set-top digital converter box, only 3 feet of cable, it
shows a perfect picture**.

Do you think replacing the RG59 with RG6 will get me the
perfect
picture other sets get? I didn't use home-runs, just
splitters and
every two splitters a signal amp, a total of three signal
amps, one
with 2 or 4 outputs, and two with 2. Would an additional
signal amp
at the start of the RG-59 also give me perfect or at least
improved reception?

BTW, I'm using an A/B switch now. I had this problem when I was
connected directly, but is there any point in getting a gold-plated
A/B switch?

Yes RG6 existed 25 years ago. You have something else wrong.
The difference in loss between 33 feet of RG59 vs. RG6 is
negligible at VHF and at most a few dB at the higher UHF
frequencies. What else is in that 33 foot span?

It's in the attic. About two feet away are two four-inch galvanized
sheet metal tubes/ducts that the bathroom fans use to blow air out of
the bathroom to the crest of the roof, but the fans are never on. The
cable doesn't go by any electric wires because the bedrooms were built
without ceiling lights. The bathroom ceiling light is maybe only two
feet away but it makes no difference if the light is on or not.

There's a 1 to 3 splitter, with one output going to another tv which
has a perfect picture, one has a terminator resistor designed for this
purpose (in an F connector), and the other output goes to the problem
tv.

The picture even from analog was perfect on most stations until analog
ended, and afaicr that was exactly when this tv picture got grainy.
But for fear this was a coincidence, I waited to ask this queestion
until I had a different tv to use here. I put that in today, and it
too has a grainy picture, even though when it was connected in the
basement, it had a smooth, perfect picture. Well, being grainy is the
only thing that's not perfect about it, afaic.


Besides being grainy, or maybe this is part of what I'm calling
graininess, the problem picture has a lot of teeny tiny white dots
sometimes just scattered in the picture and sometimes arrayed in dim
horizontal and vertical lines, about 5 lines horizontal. and 7 lines
vertical. The lines are not that straight and the vert lines move
left and right a little bit and the horiz lines up and down a little
bit. There also seem to be dots of other colors and sometimes jaggedy
dark colored lines.

The end result is a picture that's pretty good, by 1970's over-the-air
standards, and the darks are darker now than they were in June, but
it's not smooth. I can live with this of course, for years if it
works out that way, but I like to fix things.



David

On Sat, 05 Dec 2009 16:44:42 -0500, mm
wrote:

I gather from posts here that RG6 is better than RG59, is that right?

Yep. RG-6/u is generally better for most everything.

Could the use of of RG59, 33 feet, for at least one tv be responsible
for my bad reception on that tv?

If the coax cable is in good shape, hasn't been eaten by rats, mice,
squirrels, kids, vacuum cleaners, etc. and has properly attached
connectors, then there's almost no difference in performance between
RG-59 and RG-6/u. In my limited experience, lousy connector crimping
and mouse eaten cables are the usual culprits.

I'm using co-ax for distributing tv from my DVDR to TVs throughout the
house. (The DVDR tunes in the over-the-air digital signal and I have
an RF modulator to change the DVDR output to analog.

You must enjoy low quality video. It appears that you're also using
that derrangement to move audio, so the analog video is really NTSC
encoded with an approximately 4MHz maximum bandwidth. If all you have
is an analog TV, that's fine and will work, but if you're watching
this on a digital capable TV, it's wasting the capabilities of the TV.

Incidentally, thanks for leaving out all the make and model numbers,
as well as most of the numbers. That adds some credibility to my
guess work. If you want help with your SPECIFIC problem, it helps to
supply some specifics as to what manner or video problem you're seeing
and what manner of hardware you have to work with.

I did the wiring
to the tvs 25 years ago, and I used left-over and scrap co-ax, so the
co-ax is older than 25 years.

Ok, the coax is suspect. This is easier to troubleshoot by
substitution. Find a 50ft piece of decent 75 ohm coax cable. Run it
in place of the suspected 33ft piece. If it magically fixes the
problem, your old coax is history.

Also, if you have a scope and are interested in building a TDR (time
domain reflectometer), you can test the cable.
http://en.wikipedia.org/wiki/Time-domain_reflectometer
http://www.epanorama.net/circuits/tdr.html

Did they have RG-6 25 or 30 years ago?

Oh yes. It was in the original military "radio guide" MIL-HDBK-216
from WWII. The "6" means page 6 of the guide.

I didn't pay attention then so I don't know what most of it is, but
the 33 foot piece going to this one tv is RMS Electonics Inc. 59/U.

Everything was fine until the digital conversion, and now this tv that
I watch a lot shows a grainy picture. All the other tvs have great
pictures, and even for this one, when I supply a signal directly from
a set-top digital converter box, only 3 feet of cable, it shows a
perfect picture**.

I guess "grainy" means you're getting a weak signal. Well, drag one
of your other TV's over to this location and see if it's a consistent
problem. If the 2nd TV is also "grainy", then you probably have a low
signal level for some reason. Again, it can be the cable or the
connectors. A broken shield connection will still deliver a signal,
but at somewhat lower level. Also, substitute the coax with a known
good one as I previously suggested.

Do you think replacing the RG59 with RG6 will get me the perfect
picture other sets get?

Dunno. I would find the cause of the problem before ripping out the
cable. However, if it's easy to get to and doesn't make too big a
mess, it's worth a try. Either RG-59 or RG-6/u will work as you're
only using it on Channel 2 or 3 with the RF modulator.

However, if you were going to shovel the entired TV spectrum, from VHF
to the top of UHF through the cable, as you will if replace your
analog TV with a DTV, then I would use RG-6/u.

I didn't use home-runs, just splitters and
every two splitters a signal amp, a total of three signal amps, one
with 2 or 4 outputs, and two with 2.

Holdit. Any one of these can be the problem. That includes
amplifiers and splitters with unterminated outputs. First, you don't
really need all those amplifiers. Most TV's can easily handle one or
two 2 or 4 way splitters, without an amplifier. However, I have no
clue how much RF output your unspecified RF modulator belches or what
your amplfiers are doing. I also can't guess your topology (wiring
layout). My guess(tm) is that you have too many amplifiers or one of
them is unplugged or dead. Try replacing the amps with an ordinary 2
way or 4 way splitter and see if it magically fixes the problem. Also,
if you don't have a CATV signal level meter, walk the TV around to the
various amps until the bad section or amplifier is found. If you have
any unterminated outputs, kindly terminate them with a 75 ohm
terminator.

Would an additional signal amp
at the start of the RG-59 also give me perfect or at least improved
reception?

No. You already have too many amplifiers. You'll do better by
getting rid of amps or at least finding which one is the culprit. It
might still be the coax, but I'm more inclined to guess(tm) that one
of the amps if fried or sick.

**(But the set-top box isn't connected to the main antenna and
doesn't get several stations I watch, nor will it play what is
recorded on the DVDR.)

You lost me. What does this have to do with anything? Draw you
topology (wiring) and post it somewhere. Don't forget to include some
numbers.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Dec 5, 4:59*pm, Jeff Liebermann wrote:
On Sat, 05 Dec 2009 16:44:42 -0500, mm
wrote:

I gather from posts here that RG6 is better than RG59, is that right?

Yep. *RG-6/u is generally better for most everything.

Could the use of of RG59, 33 feet, for at least one tv be responsible
for my bad reception on that tv?

If the coax cable is in good shape, hasn't been eaten by rats, mice,
squirrels, kids, vacuum cleaners, etc. and has properly attached
connectors, then there's almost no difference in performance between
RG-59 and RG-6/u. *In my limited experience, lousy connector crimping
and mouse eaten cables are the usual culprits.

I'm using co-ax for distributing tv from my DVDR to TVs throughout the
house. (The DVDR tunes in the over-the-air digital signal and I have
an RF modulator to change the DVDR output to analog.

You must enjoy low quality video. *It appears that you're also using
that derrangement to move audio, so the analog video is really NTSC
encoded with an approximately 4MHz maximum bandwidth. *If all you have
is an analog TV, that's fine and will work, but if you're watching
this on a digital capable TV, it's wasting the capabilities of the TV.

Incidentally, thanks for leaving out all the make and model numbers,
as well as most of the numbers. *That adds some credibility to my
guess work. *If you want help with your SPECIFIC problem, it helps to
supply some specifics as to what manner or video problem you're seeing
and what manner of hardware you have to work with.

I did the wiring
to the tvs 25 years ago, and I used left-over and scrap co-ax, *so the
co-ax is older than 25 years.

Ok, the coax is suspect. *This is easier to troubleshoot by
substitution. *Find a 50ft piece of decent 75 ohm coax cable. *Run it
in place of the suspected 33ft piece. *If it magically fixes the
problem, your old coax is history.

Also, if you have a scope and are interested in building a TDR (time
domain reflectometer), you can test the cable.
http://en.wikipedia.org/wiki/Time-domain_reflectometer
http://www.epanorama.net/circuits/tdr.html

Did they have RG-6 25 or 30 years ago?

Oh yes. *It was in the original military "radio guide" MIL-HDBK-216
from WWII. *The "6" means page 6 of the guide.

I didn't pay attention then so I don't know what most of it is, but
the 33 foot piece going to this one tv is RMS Electonics Inc. 59/U. *

Everything was fine until the digital conversion, and now this tv that
I watch a lot shows a grainy picture. * All the other tvs have great
pictures, and even for this one, when I supply a signal directly from
a set-top digital converter box, only 3 feet of cable, it shows a
perfect picture**.

I guess "grainy" means you're getting a weak signal. *Well, drag one
of your other TV's over to this location and see if it's a consistent
problem. *If the 2nd TV is also "grainy", then you probably have a low
signal level for some reason. *Again, it can be the cable or the
connectors. *A broken shield connection will still deliver a signal,
but at somewhat lower level. *Also, substitute the coax with a known
good one as I previously suggested.

Do you think replacing the RG59 with RG6 will get me the perfect
picture other sets get?

Dunno. *I would find the cause of the problem before ripping out the
cable. *However, if it's easy to get to and doesn't make too big a
mess, it's worth a try. *Either RG-59 or RG-6/u will work as you're
only using it on Channel 2 or 3 with the RF modulator. *

However, if you were going to shovel the entired TV spectrum, from VHF
to the top of UHF through the cable, as you will if replace your
analog TV with a DTV, then I would use RG-6/u.

I didn't use home-runs, just splitters and
every two splitters a signal amp, a total of three signal amps, one
with 2 or 4 outputs, and two with 2.

Holdit. *Any one of these can be the problem. *That includes
amplifiers and splitters with unterminated outputs. *First, you don't
really need all those amplifiers. *Most TV's can easily handle one or
two 2 or 4 way splitters, without an amplifier. *However, I have no
clue how much RF output your unspecified RF modulator belches or what
your amplfiers are doing. *I also can't guess your topology (wiring
layout). *My guess(tm) is that you have too many amplifiers or one of
them is unplugged or dead. *Try replacing the amps with an ordinary 2
way or 4 way splitter and see if it magically fixes the problem. Also,
if you don't have a CATV signal level meter, walk the TV around to the
various amps until the bad section or amplifier is found. *If you have
any unterminated outputs, kindly terminate them with a 75 ohm
terminator.

Would an additional signal amp
at the start of the RG-59 also give me perfect or at least improved
reception? *

No. *You already have too many amplifiers. *You'll do better by
getting rid of amps or at least finding which one is the culprit. *It
might still be the coax, but I'm more inclined to guess(tm) that one
of the amps if fried or sick.

**(But the set-top box isn't connected to the main antenna and
doesn't get several stations I watch, nor will it play what is
recorded on the DVDR.)

You lost me. *What does this have to do with anything? *Draw you
topology (wiring) and post it somewhere. *Don't forget to include some
numbers.

--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

Try connecting each set directly by replacing the splitters with thru
connectors and see if they all work ok. This will require that you
undo and redo a bunch of connections as you check out eachset and
associated cables,, but it is the only way to be sure that your basic
components are good. I agree with other posters that bad crimp
connectios are a frequent problem. A little corrosion aftrer 25 years
may make the contact between the outer shield/aluminum ground wire to
the connector outer housing intermittent and that can do wonderous
things. If the output of the dvr is of typical levels, it should
easily drive another set 30 feet away. I have a 3-way splitter on the
output of my cable box and it drives the nearby tv as well as two
other sets 30 feet away, using a 1-3 splitter, with perfect pictures.

On Dec 5, 2:59*pm, Jeff Liebermann wrote:
....snip...
Ok, the coax is suspect. *This is easier to troubleshoot by
substitution. *Find a 50ft piece of decent 75 ohm coax cable. *Run it
in place of the suspected 33ft piece. *If it magically fixes the
problem, your old coax is history.
....snip...
Everything was fine until the digital conversion, and now this tv that
I watch a lot shows a grainy picture. * All the other tvs have great
pictures, and even for this one, when I supply a signal directly from
a set-top digital converter box, only 3 feet of cable, it shows a
perfect picture**.

I guess "grainy" means you're getting a weak signal. *Well, drag one
of your other TV's over to this location and see if it's a consistent
problem. *If the 2nd TV is also "grainy", then you probably have a low
signal level for some reason. *Again, it can be the cable or the
connectors. *A broken shield connection will still deliver a signal,
but at somewhat lower level. *Also, substitute the coax with a known
good one as I previously suggested.

....snip...
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

Sorry, for jumping in here in the way of Jeff's capable hands, but
agree with honing in on potential bad connections in that old coax.
Plus, the description of the received signal reminds me of when I had
to use an amplifier to overcome the loss from attempting to use a
splitter, only to find that some strong station was doing?? whatever
to create an overlay image on top of my viewing. Since the crystals
are so close, frame images drift over the top of each other. Looks
like the overlay dot patterns like OP described. For me, was
confirmed when one day I could actually read the call letters of the
'offending' overlay.

Also, OP said this started happening when DTV took over. That day a
lot of broadcast stations started switching their power signals
around. Even as late as October 31, they were still being shifted.
Perhaps, the band change showed up mixing, or affecting the AGC

Background of my experience with this: I added a security camera to
our home viewing. Simply popping to unused channel and I could see
who was at the front door. Sadly, I learned that RF Modulators
produce such a weak signal that I had to add an amplifier to make up
for a single one to four splitter stage. And then the problem of the
dynamic range of antenna reception reared its ugly head. And mixing
in the amp, and ad nauseum.

"mm" wrote in message
...
On Sat, 5 Dec 2009 15:52:16 -0600, "David"
wrote:

snip

dark colored lines.

The end result is a picture that's pretty good, by 1970's over-the-air
standards, and the darks are darker now than they were in June, but
it's not smooth. I can live with this of course, for years if it
works out that way, but I like to fix things.



David

Keep in mind a 3 way splitter has two 3.5db and one 7 db out.

Joe Rooney

On Sun, 6 Dec 2009 00:24:47 -0800, "Joe Rooney"
wrote:


"mm" wrote in message
.. .
On Sat, 5 Dec 2009 15:52:16 -0600, "David"
wrote:

snip

dark colored lines.

The end result is a picture that's pretty good, by 1970's over-the-air
standards, and the darks are darker now than they were in June, but
it's not smooth. I can live with this of course, for years if it
works out that way, but I like to fix things.



David

Keep in mind a 3 way splitter has two 3.5db and one 7 db out.

Aha. That would certainly account for a difference! I'll check
later today. In fact, I'll take out the splitter and connect just
the one giving me trouble.

Thanks a lot.

Joe Rooney

On Sun, 06 Dec 2009 12:03:52 -0500, mm
wrote:

On Sun, 6 Dec 2009 00:24:47 -0800, "Joe Rooney"
wrote:

Keep in mind a 3 way splitter has two 3.5db and one 7 db out.

Wrong. A splitter reduces the output by -3dB which is half the power.
The extra -0.5dB loss is from losses in the bifilar wound xformer. If
two of the ports each have half the input power, there's nothing in
the budget left for the 3rd port.

Googling for a typical 3 way splitter:
http://www.twacomm.com/catalog/model_CT413.htm?sid=1F79205DEA0D1B9FF1BF82ACDC4C33 D2
I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes
more sense. (Actually, it should be -7.0dB loss).

A 3 port looks like a tree. It starts with a two port splitter, where
one output is brought out for -3.5dB loss. The other port goes to yet
another splitter, with again divides the output in half, for -7dB from
each of the two ports.

Aha. That would certainly account for a difference! I'll check
later today. In fact, I'll take out the splitter and connect just
the one giving me trouble.

Except that you said you're using 2 and 4 way splitters, which are far
more common than a 3 way.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sat, 5 Dec 2009 20:30:48 -0800 (PST), Robert Macy
wrote:

Sorry, for jumping in here in the way of Jeff's capable hands,

Grumble...

but
agree with honing in on potential bad connections in that old coax.

There's a fairly easy way to detect bad connections. These invariably
result in coax leakage, where the coax cable magically becomes an
antenna. Find a portable TV receiver, tune it to CATV channels not
OTA (over the air) channels, and sniff around with the portable
antenna looking for leaks (actually called "ingress"). This is
roughly what the CATV people do along the distribution cables using a
pilot carrier. A broken shield, broken connector, and possbibly a
missing termination, should all show up as excessive leakage.

Personally, I prefer visual inspection, a TDR (time domain
reflectometer), signal level measurements, or just a pre-emptive
replacement.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Dec 6, 9:30*am, Jeff Liebermann wrote:
On Sat, 5 Dec 2009 20:30:48 -0800 (PST), Robert Macy

wrote:
Sorry, for jumping in here in the way of Jeff's capable hands,

Grumble...

....snip...
--
Jeff Liebermann * *
150 Felker St #D * *http://www.LearnByDestroying.com
Santa Cruz CA 95060http://802.11junk.com
Skype: JeffLiebermann * * AE6KS * *831-336-2558

LOL!

On Sun, 06 Dec 2009 09:17:54 -0800, Jeff Liebermann
wrote:

On Sun, 06 Dec 2009 12:03:52 -0500, mm
wrote:

On Sun, 6 Dec 2009 00:24:47 -0800, "Joe Rooney"
wrote:

Keep in mind a 3 way splitter has two 3.5db and one 7 db out.

Wrong. A splitter reduces the output by -3dB which is half the power.
The extra -0.5dB loss is from losses in the bifilar wound xformer. If
two of the ports each have half the input power, there's nothing in
the budget left for the 3rd port.

Googling for a typical 3 way splitter:
http://www.twacomm.com/catalog/model_CT413.htm?sid=1F79205DEA0D1B9FF1BF82ACDC4C33 D2

It says "3 way-loss 2 at 6.5 DB, 1 at 3.5 DB, 20 DB isolation DC
passive"

What does DC passive mean? Will it transmit DC power to an amplified
antenna, for example?

I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes
more sense. (Actually, it should be -7.0dB loss).

A 3 port looks like a tree. It starts with a two port splitter, where
one output is brought out for -3.5dB loss. The other port goes to yet
another splitter, with again divides the output in half, for -7dB from
each of the two ports.

Aha. That would certainly account for a difference! I'll check
later today. In fact, I'll take out the splitter and connect just
the one giving me trouble.

Except that you said you're using 2 and 4 way splitters, which are far
more common than a 3 way.

I did have a 4-way in there, but later on the slim possibility
something was wrong with the splitter, I switched and the next one I
found in my drawer was 3-way. Of course the problem pre-dates the
3-way, but I jumped to the conclusion that the 4 way might have had
something like this too.

I realize now I shouldn't have used a 4=way since i never had plans to
use more than 3 of them, but 25 years ago, I iddn't know they made
3-ways.

Thanks.

On Sat, 05 Dec 2009 14:59:33 -0800, Jeff Liebermann
wrote:

On Sat, 05 Dec 2009 16:44:42 -0500, mm
wrote:

I gather from posts here that RG6 is better than RG59, is that right?

Yep. RG-6/u is generally better for most everything.

Could the use of of RG59, 33 feet, for at least one tv be responsible
for my bad reception on that tv?

If the coax cable is in good shape, hasn't been eaten by rats, mice,
squirrels, kids, vacuum cleaners, etc. and has properly attached
connectors, then there's almost no difference in performance between
RG-59 and RG-6/u. In my limited experience, lousy connector crimping
and mouse eaten cables are the usual culprits.

Thanks. I will check both those things next time I"m in the attic,
some time this week. No problems in the part that shows.

I'm using co-ax for distributing tv from my DVDR to TVs throughout the
house. (The DVDR tunes in the over-the-air digital signal and I have
an RF modulator to change the DVDR output to analog.

You must enjoy low quality video. It appears that you're also using
that derrangement to move audio, so the analog video is really NTSC
encoded with an approximately 4MHz maximum bandwidth. If all you have
is an analog TV, that's fine and will work, but if you're watching
this on a digital capable TV, it's wasting the capabilities of the TV.

No, I can't afford any digital stuff. I've only bought one TV in the
last 37 years, but I get more than 50 of them at yard sales or out of
the trash. Some work when I get them, some I can fix, some I can't.

So I have to wait until I find some digital stuff cheap, and that's
been slowed down because as of a month ago the county trash collection
will no longer pick up tvs. People have to arrange to take them to 3
locations in the county. For many, the closest is 10 miles away.

Incidentally, thanks for leaving out all the make and model numbers,
as well as most of the numbers. That adds some credibility to my
guess work. If you want help with your SPECIFIC problem, it helps to
supply some specifics as to what manner or video problem you're seeing
and what manner of hardware you have to work with.

I should have mentioned in the first post that today I tried another
tv, and it had the same problem with the picture. OTOH, a second tv
connected to the same splitter, and also using a different splitter,
displays a perfect picture.

The two tvs with bad pictures in this room were a 12" Zenith 5 or 10
or 20 years old and 12" Magnavox with a VCR in the same age range.

I can give you model numbers if you want. But since they both give
perfect pictures when the signal is from the set-top box on top of the
tv, I didn't think the tv was the issue.

I did the wiring
to the tvs 25 years ago, and I used left-over and scrap co-ax, so the
co-ax is older than 25 years.

Ok, the coax is suspect. This is easier to troubleshoot by
substitution. Find a 50ft piece of decent 75 ohm coax cable. Run it
in place of the suspected 33ft piece. If it magically fixes the
problem, your old coax is history.

I should have thought of that. I can run it through the trap door to
the attic. No need to remove the stuff that is there. My long
pieces of coax are buried in the basement This will have to go back
on the back burner until then.

Also, if you have a scope and are interested in building a TDR (time
domain reflectometer), you can test the cable.
http://en.wikipedia.org/wiki/Time-domain_reflectometer
http://www.epanorama.net/circuits/tdr.html

I think you had the right idea the first time, substitution.

Did they have RG-6 25 or 30 years ago?

Oh yes. It was in the original military "radio guide" MIL-HDBK-216
from WWII. The "6" means page 6 of the guide.

Very interesting.

I didn't pay attention then so I don't know what most of it is, but
the 33 foot piece going to this one tv is RMS Electonics Inc. 59/U.

Everything was fine until the digital conversion, and now this tv that
I watch a lot shows a grainy picture. All the other tvs have great
pictures, and even for this one, when I supply a signal directly from
a set-top digital converter box, only 3 feet of cable, it shows a
perfect picture**.

I guess "grainy" means you're getting a weak signal. Well, drag one
of your other TV's over to this location and see if it's a consistent
problem. If the 2nd TV is also "grainy", then you probably have a low
signal level for some reason. Again, it can be the cable or the
connectors. A broken shield connection will still deliver a signal,
but at somewhat lower level. Also, substitute the coax with a known
good one as I previously suggested.

Will do.

Do you think replacing the RG59 with RG6 will get me the perfect
picture other sets get?

Dunno. I would find the cause of the problem before ripping out the
cable. However, if it's easy to get to and doesn't make too big a
mess, it's worth a try. Either RG-59 or RG-6/u will work as you're
only using it on Channel 2 or 3 with the RF modulator.

The attic gets fuller and fuller, mostly empty boxes, and more
insulation, and I'm 25 years older. It still woudln't be so hard to
replace the cable, if the substitute works right.

But it would be a lot easier, i realize now, to bypass the splitter
and connect the problem tv directly. Or to bypass the cable and run
another one temporarily outside the wall, not in it.

However, if you were going to shovel the entired TV spectrum, from VHF
to the top of UHF through the cable, as you will if replace your
analog TV with a DTV, then I would use RG-6/u.

It'll probably be 10 more years before I have a digital tv in this
room.

I didn't use home-runs, just splitters and
every two splitters a signal amp, a total of three signal amps, one
with 2 or 4 outputs, and two with 2.

Holdit. Any one of these can be the problem. That includes
amplifiers and splitters with unterminated outputs.

I don't have any unterminated outputs.

First, you don't
really need all those amplifiers.

I take it back. Now I think I only have two amplifiers. For years I
was sure that I had 3, maybe I do but I can't figure out where the
third one would be. Please forgive me. I put some of this stuff in
26 years ago and the rest 24 or 25 years ago. I plugged the amps in
and haven't had to do a thing since. At least until this fall. 24
years with no maintenance needed is pretty good.

Details about tv hookup below.**

Most TV's can easily handle one or
two 2 or 4 way splitters, without an amplifier. However, I have no
clue how much RF output your unspecified RF modulator belches or what
your amplfiers are doing.

I certainly don't know, but it's conceivable that the RF modulator
puts out much more than the various VCR's I used did, but all I did
about 18 months ago was replace a mediocre VCR with a Philips
DVDR3576H DVD recorder with 160 Gig hard drive, and add a RF modulator
that cost about 18 dollars on Amazon, and everything worked and I
didn't verify any of the outlying circuitry or tvs. I'm 99% sure even
this tv gave no problems then , 18 months ago, and only gave problems
last June when the analog stations went away. I had been watching
analog for a whole year even after I had a digital tuner, because
channel surfing is much quicker in analog.

I also can't guess your topology (wiring
layout). My guess(tm) is that you have too many amplifiers or one of
them is unplugged or dead.

If one were unplugged, at least one other tv would have little or no
picture. I think. Since every amp suplies signal to at least two
tv's. But after I try substituting the cable, I will look again at
the main amp.

Try replacing the amps with an ordinary 2
way or 4 way splitter and see if it magically fixes the problem. Also,

Not likely, because I didn't put the amp in until the signal was too
weak and the picture was washed out. Only if the RF modulator puts
out a substantially stronger signal than the first VCR did. But I
appreciate the suggestion and will try it if all else fails.

if you don't have a CATV signal level meter, walk the TV around to the
various amps until the bad section or amplifier is found. If you have
any unterminated outputs, kindly terminate them with a 75 ohm
terminator.

Would an additional signal amp
at the start of the RG-59 also give me perfect or at least improved
reception?

No. You already have too many amplifiers. You'll do better by
getting rid of amps or at least finding which one is the culprit. It
might still be the coax, but I'm more inclined to guess(tm) that one
of the amps if fried or sick.

But every amp supplies signal to more than one tv, and only this one
tv has a problem.

**(But the set-top box isn't connected to the main antenna and
doesn't get several stations I watch, nor will it play what is
recorded on the DVDR.)

You lost me. What does this have to do with anything? Draw you

Sorry. Not important. Never mind.

topology (wiring) and post it somewhere. Don't forget to include some
numbers.

I'm good at neither drawing nor posting. Last time I tried posting, it
was a time-consuming failure. But I think I can describe it clearly.

**I was running 8 tvs but now I'm running 7 off of the DVDR, formerly
the VCR, and I never put in an amplifier until I put in another
splitter, ran co-ax to another room and connected a tv and saw that
the picture was washed out.

The VCR, now DVDR, is in my bedroom. (I used to have Comcast cable
that went to the VCR.) The output from the DVDR goes to the closet
where there is a 4 way amplifier, with one output terminated, one to
the tv right there in that bedrroom, one to the attic (A), and one to
the first floor & basement (B).

(A) goes into the attic and 20 feet away splits 3 ways, one
terminated***, one to the tv in the bathrom which has a perfect
picture, and one to the tv in the office/spare bedroom, with the
problem picture. ***When I spent more time in the attic, I had a tv
stored up there, that I watched, and it used the now-terminated
output.

(B) goes to the first floor and a two way splitter, one output to the
living-room tv, and one output to the basement. In the basement
family room is a another amplifier with two outputs, one output to the
family room tv and one to the laundry room.

In the laundry room is another splitter, one output to the laundry
room tv (I needed a place to store an extra tv anyhow, so I might as
well connect it) and one output upstairs to the kitchen.

7 tvs are connected, an eighth used to be.

On Sat, 5 Dec 2009 20:12:17 -0800 (PST), "hr(bob) "
wrote:


Try connecting each set directly by replacing the splitters with thru
connectors and see if they all work ok. This will require that you
undo and redo a bunch of connections as you check out eachset and
associated cables,, but it is the only way to be sure that your basic
components are good. I agree with other posters that bad crimp
connectios are a frequent problem. A little corrosion aftrer 25 years
may make the contact between the outer shield/aluminum ground wire to
the connector outer housing intermittent and that can do wonderous
things. If the output of the dvr is of typical levels, it should
easily drive another set 30 feet away. I have a 3-way splitter on the
output of my cable box and it drives the nearby tv as well as two
other sets 30 feet away, using a 1-3 splitter, with perfect pictures.

When I first got cable tv -- I don't have it anymore --, the guy ran
the cable in through the floor of the close, which overhangs the first
floor. The cable box connected to a channel control dial via a cable,
no infra-red, and I told him I wanted to keep the box in the closet,
out of my way.

He said he wasnt' sure if the tv could that far from the box. The tv
was about 6 feet away.

Later when I connected the first remote tv and was running the co-ax
through the basement ceiling, so for some reason it was 3 times as
long as it would be when I was done, it was about 120 feet and it
still worked fine, but he thought 6 might be too much. (I didnt' get
the slightest impression he was looking for a tip for him to make a
wire 7 feet long, but maybe I'm dense and that's what he wanted??
That didn't occur to me until just now.)

On Sun, 06 Dec 2009 15:04:23 -0500, mm
wrote:

Googling for a typical 3 way splitter:
http://www.twacomm.com/catalog/model_CT413.htm?sid=1F79205DEA0D1B9FF1BF82ACDC4C33 D2

It says "3 way-loss 2 at 6.5 DB, 1 at 3.5 DB, 20 DB isolation DC
passive"

It should be 7dB, not 6.5dB but close enough.

What does DC passive mean? Will it transmit DC power to an amplified
antenna, for example?

Yep. DC passive means that there is DC continuity between the ports.
--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Joe Rooney wrote:

Keep in mind a 3 way splitter has two 3.5db and one 7 db out.


Not all of them. If you know where to look, you can find three way
splitters with -5 dB at each port. They were in use in CATV in the
early -80s. I kept a small stock of them at the United Video system in
Delhi Township (Cincinatti, Ohio) for installs where the standard
version wouldn't work.


--
Offworld checks no longer accepted!

Jeff Liebermann wrote:

On Sun, 06 Dec 2009 12:03:52 -0500, mm
wrote:

On Sun, 6 Dec 2009 00:24:47 -0800, "Joe Rooney"
wrote:

Keep in mind a 3 way splitter has two 3.5db and one 7 db out.

Wrong. A splitter reduces the output by -3dB which is half the power.
The extra -0.5dB loss is from losses in the bifilar wound xformer. If
two of the ports each have half the input power, there's nothing in
the budget left for the 3rd port.


Part of the extra .5 dB loss is in the cast aluminum 'F' connectors.
I ran Q. A. I ran tests on hundreds of samples to qualify them for our
MSO to purchase the best quality we could find. We bought splitters by
the thousands, and coax by the pallet

Also, eight way splitters are listed at -10 dB, not 10.5.



--
Offworld checks no longer accepted!

mm wrote:

On Sun, 06 Dec 2009 09:17:54 -0800, Jeff Liebermann
wrote:

On Sun, 06 Dec 2009 12:03:52 -0500, mm
wrote:

On Sun, 6 Dec 2009 00:24:47 -0800, "Joe Rooney"
wrote:

Keep in mind a 3 way splitter has two 3.5db and one 7 db out.

Wrong. A splitter reduces the output by -3dB which is half the power.
The extra -0.5dB loss is from losses in the bifilar wound xformer. If
two of the ports each have half the input power, there's nothing in
the budget left for the 3rd port.

Googling for a typical 3 way splitter:
http://www.twacomm.com/catalog/model_CT413.htm?sid=1F79205DEA0D1B9FF1BF82ACDC4C33 D2

It says "3 way-loss 2 at 6.5 DB, 1 at 3.5 DB, 20 DB isolation DC
passive"

What does DC passive mean? Will it transmit DC power to an amplified
antenna, for example?


Yes. Some splitters will pass DC, usually only to one port.

The 20 dB isolation means that the return loss is more than 20 dB.
This is to prevent the local oscillator from one TV causing interference
to another TV. I was the engineer at a CATV system with over 10,000
active drops. There are hundreds of myths and half truths about the
hardware used for CATV systems.


I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes
more sense. (Actually, it should be -7.0dB loss).


An ideal splitter would be 3 dB, 6 db, 9 db etc., but connector
losses, and to a smaller extent, core losses in the broadband
transformers add the fractional losses.


A 3 port looks like a tree. It starts with a two port splitter, where
one output is brought out for -3.5dB loss. The other port goes to yet
another splitter, with again divides the output in half, for -7dB from
each of the two ports.

Aha. That would certainly account for a difference! I'll check
later today. In fact, I'll take out the splitter and connect just
the one giving me trouble.

Except that you said you're using 2 and 4 way splitters, which are far
more common than a 3 way.

I did have a 4-way in there, but later on the slim possibility
something was wrong with the splitter, I switched and the next one I
found in my drawer was 3-way. Of course the problem pre-dates the
3-way, but I jumped to the conclusion that the 4 way might have had
something like this too.

I realize now I shouldn't have used a 4 way since i never had plans to
use more than 3 of them, but 25 years ago, I iddn't know they made
3-ways.

Thanks.


--
Offworld checks no longer accepted!

mm wrote:

On Sat, 5 Dec 2009 20:12:17 -0800 (PST), "hr(bob) "
wrote:


Try connecting each set directly by replacing the splitters with thru
connectors and see if they all work ok. This will require that you
undo and redo a bunch of connections as you check out eachset and
associated cables,, but it is the only way to be sure that your basic
components are good. I agree with other posters that bad crimp
connectios are a frequent problem. A little corrosion aftrer 25 years
may make the contact between the outer shield/aluminum ground wire to
the connector outer housing intermittent and that can do wonderous
things. If the output of the dvr is of typical levels, it should
easily drive another set 30 feet away. I have a 3-way splitter on the
output of my cable box and it drives the nearby tv as well as two
other sets 30 feet away, using a 1-3 splitter, with perfect pictures.

When I first got cable tv -- I don't have it anymore --, the guy ran
the cable in through the floor of the close, which overhangs the first
floor. The cable box connected to a channel control dial via a cable,
no infra-red, and I told him I wanted to keep the box in the closet,
out of my way.

He said he wasnt' sure if the tv could that far from the box. The tv
was about 6 feet away.

Later when I connected the first remote tv and was running the co-ax
through the basement ceiling, so for some reason it was 3 times as
long as it would be when I was done, it was about 120 feet and it
still worked fine, but he thought 6 might be too much. (I didnt' get
the slightest impression he was looking for a tip for him to make a
wire 7 feet long, but maybe I'm dense and that's what he wanted??
That didn't occur to me until just now.)


Cable installers are first tier techs. They aren't trained to think,
or troubleshoot. The standard cable between the TV and the converter
was three feet, because that worked with 99% of the TVs in use.

You should see the calculations needed to design a trunkline or
feeder, or even worse, to interconnect two CATV systems. I wrote
software in the mid '80s to allow me to select the hardline by size and
vendor, along with the passives. Our designs called for a minimum of
+10 dB at the tap, but to minimize the number of trunk or bridger
amplifiers. You used a strand map to get accurate distances to
calculate the cable losses, then selected the tap required. That added a
block of loss to the feeder. Each calculation was based on the ones
before it.


--
Offworld checks no longer accepted!

Jeff Liebermann wrote:

On Sat, 5 Dec 2009 20:30:48 -0800 (PST), Robert Macy
wrote:

Sorry, for jumping in here in the way of Jeff's capable hands,

Grumble...

but
agree with honing in on potential bad connections in that old coax.

There's a fairly easy way to detect bad connections. These invariably
result in coax leakage, where the coax cable magically becomes an
antenna. Find a portable TV receiver, tune it to CATV channels not
OTA (over the air) channels, and sniff around with the portable
antenna looking for leaks (actually called "ingress"). This is
roughly what the CATV people do along the distribution cables using a
pilot carrier. A broken shield, broken connector, and possbibly a
missing termination, should all show up as excessive leakage.


Ingression is external signals getting into the CATV plant. You are
describing radiation' where the signal is lost to being radiated from
the outer conductor, due to poor connections. It is monitored on a
continuous basis on most cable systems using 'Sniffer' or other brands
of monitoring equipment. While the signal is on the video carrier
frequency, it is FM modulated with annoying audio to make it easy to
identify.



Personally, I prefer visual inspection, a TDR (time domain
reflectometer), signal level measurements, or just a pre-emptive
replacement.


Those are OK if you can shut a system down for repairs. Poor
connections in the trunkline can be detected by reading the voltage drop
between the coax and the amplifier housing, splice block or any other
splice in any powered cable. 60 volts modified sine wave AC @ 30 amps
from a CVT doesn't tolerate much resistance without causing hum
modulation or burning up a connector.

--
Offworld checks no longer accepted!

On Sun, 06 Dec 2009 22:51:17 -0500, "Michael A. Terrell"
wrote:

Part of the extra .5 dB loss is in the cast aluminum 'F' connectors.
I ran Q. A. I ran tests on hundreds of samples to qualify them for our
MSO to purchase the best quality we could find. We bought splitters by
the thousands, and coax by the pallet

Also, eight way splitters are listed at -10 dB, not 10.5.

Agreed. However, I never had much trouble with the aluminium F
connectors. It was the chrome plated zinc castings that drove me
nuts. The RF skin depth at 1GHz was terrible making the connectors
rather lossy. Combined with an aluminum F connector, I had a few
millivolts of electrolysis and noise.

For entertainment, I like to string all the adapters in my collection
in series, and measure the loss. According to numerous luminaries,
the attenuation would be attrocious, sky high, dismal, or anything
except nominal. I don't have photos of my last song and dance in
front of the local radio clubs, but one person agreed to reproduce the
experiment with decent test equipment:
http://802.11junk.com/jeffl/antennas/connector-loss/
The display photos are rather difficult to read. The loss through
about 20 adapters is about -0.3dB at 450MHz and -2.0dB at 2.4GHz.
That's approximately the loss of an equivalent length of LMR-240. I've
done similar tests with assorted F adapters with similar results. The
chain a created for the local radio clubs was about 6ft long. I got
lazy and just used a wattmeter at each end of the coax, and a handheld
radio. Hardly any loss at 446MHz.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 06 Dec 2009 23:11:22 -0500, "Michael A. Terrell"
wrote:

Ingression is external signals getting into the CATV plant. You are
describing radiation' where the signal is lost to being radiated from
the outer conductor, due to poor connections. It is monitored on a
continuous basis on most cable systems using 'Sniffer' or other brands
of monitoring equipment. While the signal is on the video carrier
frequency, it is FM modulated with annoying audio to make it easy to
identify.

Well, the leak or ingress goes both ways. While ingress from ham,
commercial, and broadcast radio xmitters are irritating, the
regulatory requirement is to prevent cable leakage from interfering
with public safety, aircraft, and of course, OTA broadcast. Lots of
nice toys to measure this leakage:
http://www.trilithic.com/Broadband%20Instruments

Personally, I prefer visual inspection, a TDR (time domain
reflectometer), signal level measurements, or just a pre-emptive
replacement.

Those are OK if you can shut a system down for repairs. Poor
connections in the trunkline can be detected by reading the voltage drop
between the coax and the amplifier housing, splice block or any other
splice in any powered cable. 60 volts modified sine wave AC @ 30 amps
from a CVT doesn't tolerate much resistance without causing hum
modulation or burning up a connector.

Ummm... the OP is trying to troubleshoot his home installation, not
the trunk line (or cable drop). I think it's a safe bet that he can
unplug his spaghetti without difficulties.


--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

Jeff Liebermann wrote:

On Sun, 06 Dec 2009 23:11:22 -0500, "Michael A. Terrell"
wrote:

Ingression is external signals getting into the CATV plant. You are
describing radiation' where the signal is lost to being radiated from
the outer conductor, due to poor connections. It is monitored on a
continuous basis on most cable systems using 'Sniffer' or other brands
of monitoring equipment. While the signal is on the video carrier
frequency, it is FM modulated with annoying audio to make it easy to
identify.

Well, the leak or ingress goes both ways. While ingress from ham,
commercial, and broadcast radio xmitters are irritating, the
regulatory requirement is to prevent cable leakage from interfering
with public safety, aircraft, and of course, OTA broadcast. Lots of
nice toys to measure this leakage:
http://www.trilithic.com/Broadband%20Instruments


The idiot manager of one system ordered the wrong midband modulator
that was right in the aircraft band. Rather than admit it, over 10,000
converters had to be modified to tune the new channel. It was used to
add 'The nashville Network' which had just been launched. The system was
in the Cincinnati area where people claimed that they didn't listen to
'**** kicking music'. I tested the mew modulator & c-band equipment for
less than 30 seconds, and after 2 am. We had over 100 phone calls
waiting the next morning, wanting to know when it would be back.



Personally, I prefer visual inspection, a TDR (time domain
reflectometer), signal level measurements, or just a pre-emptive
replacement.

Those are OK if you can shut a system down for repairs. Poor
connections in the trunkline can be detected by reading the voltage drop
between the coax and the amplifier housing, splice block or any other
splice in any powered cable. 60 volts modified sine wave AC @ 30 amps
from a CVT doesn't tolerate much resistance without causing hum
modulation or burning up a connector.

Ummm... the OP is trying to troubleshoot his home installation, not
the trunk line (or cable drop). I think it's a safe bet that he can
unplug his spaghetti without difficulties.


Then it is very unlikely he will have access to a TDR, sniffer or any
other equipment. Even a field strength meter isn't likely.


--
Offworld checks no longer accepted!

Jeff Liebermann wrote:

On Sun, 06 Dec 2009 22:51:17 -0500, "Michael A. Terrell"
wrote:

Part of the extra .5 dB loss is in the cast aluminum 'F' connectors.
I ran Q. A. I ran tests on hundreds of samples to qualify them for our
MSO to purchase the best quality we could find. We bought splitters by
the thousands, and coax by the pallet

Also, eight way splitters are listed at -10 dB, not 10.5.

Agreed. However, I never had much trouble with the aluminium F
connectors. It was the chrome plated zinc castings that drove me
nuts. The RF skin depth at 1GHz was terrible making the connectors
rather lossy. Combined with an aluminum F connector, I had a few
millivolts of electrolysis and noise.


the tap plates were cast aluminum if they were Jerrold, or plated
brass threads bolted to an aluminum plate in Lindsay taps. Both cause
problems in areas where road salt was used. Just as bad were the
unplated brass cable connectors someone tried to sell us.

For entertainment, I like to string all the adapters in my collection
in series, and measure the loss. According to numerous luminaries,
the attenuation would be attrocious, sky high, dismal, or anything
except nominal. I don't have photos of my last song and dance in
front of the local radio clubs, but one person agreed to reproduce the
experiment with decent test equipment:
http://802.11junk.com/jeffl/antennas/connector-loss/


Run the tests again after a 48 hour salt spray test.


The display photos are rather difficult to read. The loss through
about 20 adapters is about -0.3dB at 450MHz and -2.0dB at 2.4GHz.
That's approximately the loss of an equivalent length of LMR-240. I've
done similar tests with assorted F adapters with similar results. The
chain a created for the local radio clubs was about 6ft long. I got
lazy and just used a wattmeter at each end of the coax, and a handheld
radio. Hardly any loss at 446MHz.


--
Offworld checks no longer accepted!

On Mon, 07 Dec 2009 02:59:30 -0500, "Michael A. Terrell"
wrote:

the tap plates were cast aluminum if they were Jerrold, or plated
brass threads bolted to an aluminum plate in Lindsay taps. Both cause
problems in areas where road salt was used. Just as bad were the
unplated brass cable connectors someone tried to sell us.

Again, this is for outdoor use. The OP is doing indoor.

http://802.11junk.com/jeffl/antennas/connector-loss/

Run the tests again after a 48 hour salt spray test.

http://en.wikipedia.org/wiki/Salt_spray_test

Actually, I have. I used to design marine radios and the salt fog
test was one of the hazards of the business. None of the equipment
survived 100%. We were just checking for problems that might occur in
a marine atmosphere. As I recall, the silver plated brass connectors
did quite well, while the cadmium plated pot metal died a horrible
death. Dissimilar metals and connector materials were also bad.
Unless you watch TV in the shower, I don't think any of these will be
a problem with an indoor installation.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Sun, 06 Dec 2009 20:49:12 -0800, Jeff Liebermann
wrote:

On Sun, 06 Dec 2009 22:51:17 -0500, "Michael A. Terrell"
wrote:

Part of the extra .5 dB loss is in the cast aluminum 'F' connectors.
I ran Q. A. I ran tests on hundreds of samples to qualify them for our
MSO to purchase the best quality we could find. We bought splitters by
the thousands, and coax by the pallet

Also, eight way splitters are listed at -10 dB, not 10.5.

Agreed. However, I never had much trouble with the aluminium F
connectors. It was the chrome plated zinc castings that drove me
nuts. The RF skin depth at 1GHz was terrible making the connectors
rather lossy. Combined with an aluminum F connector, I had a few
millivolts of electrolysis and noise.

So is there any value in getting gold-plated F connectors (if they
have them) or gold-plated A/B switches (which I know they sell)?

It's the A/B switch I'm particularly curious about because at one
store, that was all they had, and some antenna signals are so weak, I
figured any little thing might help.


Or other gold plated connectors?

On Mon, 07 Dec 2009 13:15:19 -0500, mm
wrote:

So is there any value in getting gold-plated F connectors (if they
have them) or gold-plated A/B switches (which I know they sell)?

No. The plating is so thin, that at UHF frequencies, the skin depth
is less than the plating depth. If you want good RF conductivity, get
silver plated connectors. The real problem with gold is dissimilar
metals. Although gold will not corrode, oxidize, or rot, it will
create an electrolytic junction when wet. The result is some noise,
and possibly some corrosion of the other junction metal. What that
means is that gold is a fair idea if you use all gold connectors,
everywhere. It's not so great an idea if you mix materials.

However, that's really only for exterior installations, where water
can get into the connectors and devices. For indoor use, it's not so
much an issue unless you live in the tropics, on a boat, or in a
swamp.

It's the A/B switch I'm particularly curious about because at one
store, that was all they had, and some antenna signals are so weak, I
figured any little thing might help.

Or other gold plated connectors?

Ok, so we're off cable TV and onto OTA (over the air) issues.

The biggest improvements you do for signal strength are (in order of
importance):
1. Location, location, location, location, line of sight, etc.
2. Selection, design and construction of the antenna(s).
3. A tower mounted amplifier.
4. Everything else.
If you've done the first 3 items, to the best your abilities and
finances, then tinkering with plating materials and A-B switches is a
waste of time and money.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

On Mon, 07 Dec 2009 11:46:16 -0800, Jeff Liebermann
wrote:

On Mon, 07 Dec 2009 13:15:19 -0500, mm
wrote:

So is there any value in getting gold-plated F connectors (if they
have them) or gold-plated A/B switches (which I know they sell)?

No. The plating is so thin, that at UHF frequencies, the skin depth
is less than the plating depth. If you want good RF conductivity, get
silver plated connectors. The real problem with gold is dissimilar
metals. Although gold will not corrode, oxidize, or rot, it will
create an electrolytic junction when wet. The result is some noise,
and possibly some corrosion of the other junction metal. What that
means is that gold is a fair idea if you use all gold connectors,
everywhere. It's not so great an idea if you mix materials.

However, that's really only for exterior installations, where water
can get into the connectors and devices. For indoor use, it's not so
much an issue unless you live in the tropics, on a boat, or in a
swamp.

I've been told it's a swamp, but I disagreed.

It's the A/B switch I'm particularly curious about because at one
store, that was all they had, and some antenna signals are so weak, I
figured any little thing might help.

Or other gold plated connectors?

Ok, so we're off cable TV and onto OTA (over the air) issues.

The biggest improvements you do for signal strength are (in order of
importance):
1. Location, location, location, location, line of sight, etc.
2. Selection, design and construction of the antenna(s).
3. A tower mounted amplifier.
4. Everything else.
If you've done the first 3 items, to the best your abilities and
finances, then tinkering with plating materials and A-B switches is a
waste of time and money.

Good to know. Thanks.

On Mon, 07 Dec 2009 02:56:48 -0500, "Michael A. Terrell"
wrote:

The idiot manager of one system ordered the wrong midband modulator
that was right in the aircraft band. Rather than admit it, over 10,000
converters had to be modified to tune the new channel.

Ouch. However, the aircraft band is from 108 to 136Mhz. That covers
channels 98, 99, 14, 15, and 16 that have to be protected. Comcast is
using 14 and 15 locally, but I've noticed that the signal levels are
much lower than the adjacent channels.

It was used to
add 'The nashville Network' which had just been launched. The system was
in the Cincinnati area where people claimed that they didn't listen to
'**** kicking music'. I tested the mew modulator & c-band equipment for
less than 30 seconds, and after 2 am. We had over 100 phone calls
waiting the next morning, wanting to know when it would be back.

Chuckle. There's no accounting for taste. For the last year or so,
I've been erratically trying to convince DirecTV to carry UCTV:
http://www.uctv.tv
It's currently carried by Dish and Comcast locally, but not DirecTV.
So far, my efforts have been futile. So, I watch UCTV on the
computah.

Ummm... the OP is trying to troubleshoot his home installation, not
the trunk line (or cable drop). I think it's a safe bet that he can
unplug his spaghetti without difficulties.

Then it is very unlikely he will have access to a TDR, sniffer or any
other equipment. Even a field strength meter isn't likely.

If he can borrow an oscilloscope, a TDR is very easy to build. I've
built several similar to:
http://www.epanorama.net/circuits/tdr.html
If he knew the test frequency, a simple scanner with aircraft band
should work. Every cable operator seems to use a different frequency.
I usually find it by connecting my scanner to the cable, and scanning
the aircraft band for the obnoxious tones.

--
# Jeff Liebermann 150 Felker St #D Santa Cruz CA 95060
# 831-336-2558
# http://802.11junk.com
# http://www.LearnByDestroying.com AE6KS

Jeff Liebermann wrote:

On Mon, 07 Dec 2009 02:56:48 -0500, "Michael A. Terrell"
wrote:

The idiot manager of one system ordered the wrong midband modulator
that was right in the aircraft band. Rather than admit it, over 10,000
converters had to be modified to tune the new channel.

Ouch. However, the aircraft band is from 108 to 136Mhz. That covers
channels 98, 99, 14, 15, and 16 that have to be protected. Comcast is
using 14 and 15 locally, but I've noticed that the signal levels are
much lower than the adjacent channels.

It was used to
add 'The nashville Network' which had just been launched. The system was
in the Cincinnati area where people claimed that they didn't listen to
'**** kicking music'. I tested the mew modulator & c-band equipment for
less than 30 seconds, and after 2 am. We had over 100 phone calls
waiting the next morning, wanting to know when it would be back.

Chuckle. There's no accounting for taste. For the last year or so,
I've been erratically trying to convince DirecTV to carry UCTV:
http://www.uctv.tv
It's currently carried by Dish and Comcast locally, but not DirecTV.
So far, my efforts have been futile. So, I watch UCTV on the
computah.


The system added TNN at my insistence. We picked up about 500 new
customers by adding it. The number one country music station in the US
was in Cincinnati for several years.


Ummm... the OP is trying to troubleshoot his home installation, not
the trunk line (or cable drop). I think it's a safe bet that he can
unplug his spaghetti without difficulties.

Then it is very unlikely he will have access to a TDR, sniffer or any
other equipment. Even a field strength meter isn't likely.

If he can borrow an oscilloscope, a TDR is very easy to build. I've
built several similar to:
http://www.epanorama.net/circuits/tdr.html


I preferred my homebrew return loss bridge. I used a surplus video
modulator module for the Atari 2600, and built the bridge in a Pomona
diecast box. It was a lot more useful than a TDR in troubleshooting the
MATV systems in dozens of schools.


If he knew the test frequency, a simple scanner with aircraft band
should work. Every cable operator seems to use a different frequency.
I usually find it by connecting my scanner to the cable, and scanning
the aircraft band for the obnoxious tones.


United Video always used the video carrier frequency of the first
channel past what the system used.


--
Offworld checks no longer accepted!

In message , Michael A.
Terrell writes


The 20 dB isolation means that the return loss is more than 20 dB.

No it doesn't. It means that the isolation - the loss between two
outputs (with the input terminated) - is 20dB.

This is to prevent the local oscillator from one TV causing interference
to another TV.

True - but, more generally, it is to minimise the effects of something
connected to one output affecting another output. As well as protecting
against local oscillators, it also protects against incorrect loading
(ie if an output port is not correctly terminated in a 75 ohm load). It
should not matter (too much) if an output is left open circuit, short
circuited, has a length of cable connected to it but going nowhere, etc
etc.

I was the engineer at a CATV system with over 10,000
active drops. There are hundreds of myths and half truths about the
hardware used for CATV systems.

Was your statement above (about RLR) one of these? [Sorry. The Devil
made me say that! ;o))]

I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes
more sense. (Actually, it should be -7.0dB loss).

While most 3-ways are typically 3.5/7/7, there are one or two around
with equal outputs, of appx 5.5dB (although, personally, I can't really
see much need for them).
--
Ian

Ian Jackson wrote:

In message , Michael A.
Terrell writes


The 20 dB isolation means that the return loss is more than 20 dB.

No it doesn't. It means that the isolation - the loss between two
outputs (with the input terminated) - is 20dB.


Sigh. How do you think you measure that isolation?


This is to prevent the local oscillator from one TV causing interference
to another TV.

True - but, more generally, it is to minimise the effects of something
connected to one output affecting another output.


What are you connecting that doesn't have a TV tuner? FM radios are
supposed to use a single port -20 dB tap.


As well as protecting
against local oscillators, it also protects against incorrect loading
(ie if an output port is not correctly terminated in a 75 ohm load). It
should not matter (too much) if an output is left open circuit, short
circuited, has a length of cable connected to it but going nowhere, etc
etc.


Unterminated ports are not allowed in properly designed systems.
PERIOD.


I was the engineer at a CATV system with over 10,000
active drops. There are hundreds of myths and half truths about the
hardware used for CATV systems.

Was your statement above (about RLR) one of these? [Sorry. The Devil
made me say that! ;o))]

I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes
more sense. (Actually, it should be -7.0dB loss).

While most 3-ways are typically 3.5/7/7, there are one or two around
with equal outputs, of appx 5.5dB (although, personally, I can't really
see much need for them).


You would, if the use of the 3.5/7/7 would require a second drop from
the line tap on the street.


--
Offworld checks no longer accepted!

In message , Michael A.
Terrell writes

Ian Jackson wrote:

In message , Michael A.
Terrell writes


The 20 dB isolation means that the return loss is more than 20 dB.

No it doesn't. It means that the isolation - the loss between two
outputs (with the input terminated) - is 20dB.

Sigh. How do you think you measure that isolation?

Sigh as much as you like - isolation and RLR are definitely NOT the same
thing, and you don't measure them in the same way.

This is to prevent the local oscillator from one TV causing interference
to another TV.

True - but, more generally, it is to minimise the effects of something
connected to one output affecting another output.

What are you connecting that doesn't have a TV tuner? FM radios are
supposed to use a single port -20 dB tap.

That could make the FM level uncomfortably low. It's better to separate
the FM from the TV signals via a bandpass diplexer filter. This is/was
common practice in Europe. Of course, in the USA, you have always had
your Channel 5 (running right up to the LF end of the FM band). Also,
these days, you could have digital TV signals starting immediately above
the FM (and still meeting the 'no interference' regulations for Air
Traffic Control radio. Do any cable systems still actually carry FM
radio?

As well as protecting
against local oscillators, it also protects against incorrect loading
(ie if an output port is not correctly terminated in a 75 ohm load). It
should not matter (too much) if an output is left open circuit, short
circuited, has a length of cable connected to it but going nowhere, etc
etc.

Unterminated ports are not allowed in properly designed systems.
PERIOD.

They may be installed correctly terminated, but you can bet your bottom
dollar a lot won't stay that way!

I was the engineer at a CATV system with over 10,000
active drops. There are hundreds of myths and half truths about the
hardware used for CATV systems.

Was your statement above (about RLR) one of these? [Sorry. The Devil
made me say that! ;o))]

I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes
more sense. (Actually, it should be -7.0dB loss).

While most 3-ways are typically 3.5/7/7, there are one or two around
with equal outputs, of appx 5.5dB (although, personally, I can't really
see much need for them).


You would, if the use of the 3.5/7/7 would require a second drop from
the line tap on the street.

When I said "much use", I meant "MUCH use". While a computerized CATV
system planner may flag up an out-of-spec condition, in practice, there
may be less than 1dB difference between a nominal 5.5 and 7dB.
--
Ian

Ian Jackson wrote:

In message , Michael A.
Terrell writes

Ian Jackson wrote:

In message , Michael A.
Terrell writes


The 20 dB isolation means that the return loss is more than 20 dB.

No it doesn't. It means that the isolation - the loss between two
outputs (with the input terminated) - is 20dB.

Sigh. How do you think you measure that isolation?

Sigh as much as you like - isolation and RLR are definitely NOT the same
thing, and you don't measure them in the same way.


You use the same equipment, but connect the ports in a different
order.


This is to prevent the local oscillator from one TV causing interference
to another TV.

True - but, more generally, it is to minimise the effects of something
connected to one output affecting another output.

What are you connecting that doesn't have a TV tuner? FM radios are
supposed to use a single port -20 dB tap.

That could make the FM level uncomfortably low.


A 0 dB or higer signal will overload the front end of a FM radio. O
dBM is 1000 microvolts @ 75 Ohms. FM radios are supposed to work at full
quieting 10 microvolts. Some of the -20 dB taps were labeled as FM Taps
and were supposed to have a bandpass filter on the output port but none
of the ones I tested in the lab did.


It's better to separate
the FM from the TV signals via a bandpass diplexer filter. This is/was
common practice in Europe. Of course, in the USA, you have always had
your Channel 5 (running right up to the LF end of the FM band).


No, it is Channel 6, with the aural carrier at 87.7 MHz. That is .3
Mhz below the bottom edge of the 88 to 108 MHz FM Broadcast band.


Also,
these days, you could have digital TV signals starting immediately above
the FM (and still meeting the 'no interference' regulations for Air
Traffic Control radio. Do any cable systems still actually carry FM
radio?


Are you kidding? They were dropped as soon as the franchises stopped
asking for FM and wanted more video channels. They gained three midband
channels without rebuilding the system.


As well as protecting
against local oscillators, it also protects against incorrect loading
(ie if an output port is not correctly terminated in a 75 ohm load). It
should not matter (too much) if an output is left open circuit, short
circuited, has a length of cable connected to it but going nowhere, etc
etc.

Unterminated ports are not allowed in properly designed systems.
PERIOD.

They may be installed correctly terminated, but you can bet your bottom
dollar a lot won't stay that way!


Not if it's maintained by morons. But then, those systems were never
in spec.



I was the engineer at a CATV system with over 10,000
active drops. There are hundreds of myths and half truths about the
hardware used for CATV systems.

Was your statement above (about RLR) one of these? [Sorry. The Devil
made me say that! ;o))]

I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes
more sense. (Actually, it should be -7.0dB loss).

While most 3-ways are typically 3.5/7/7, there are one or two around
with equal outputs, of appx 5.5dB (although, personally, I can't really
see much need for them).


You would, if the use of the 3.5/7/7 would require a second drop from
the line tap on the street.

When I said "much use", I meant "MUCH use". While a computerized CATV
system planner may flag up an out-of-spec condition, in practice, there
may be less than 1dB difference between a nominal 5.5 and 7dB.


So? If the franchise calls for all drops to be above 0 dB, one dB is
out of spec.


--
Offworld checks no longer accepted!

Ian Jackson wrote:

In message , Michael A.
Terrell writes

Ian Jackson wrote:

In message , Michael A.
Terrell writes


The 20 dB isolation means that the return loss is more than 20 dB.

No it doesn't. It means that the isolation - the loss between two
outputs (with the input terminated) - is 20dB.

Sigh. How do you think you measure that isolation?

Sigh as much as you like - isolation and RLR are definitely NOT the same
thing, and you don't measure them in the same way.


You use the same equipment, but connect the ports in a different
order.


This is to prevent the local oscillator from one TV causing interference
to another TV.

True - but, more generally, it is to minimise the effects of something
connected to one output affecting another output.

What are you connecting that doesn't have a TV tuner? FM radios are
supposed to use a single port -20 dB tap.

That could make the FM level uncomfortably low.


A 0 dB or higer signal will overload the front end of a FM radio. O
dBM is 1000 microvolts @ 75 Ohms. FM radios are supposed to work at full
quieting 10 microvolts. Some of the -20 dB taps were labeled as FM Taps
and were supposed to have a bandpass filter on the output port but none
of the ones I tested in the lab did.


It's better to separate
the FM from the TV signals via a bandpass diplexer filter. This is/was
common practice in Europe. Of course, in the USA, you have always had
your Channel 5 (running right up to the LF end of the FM band).


No, it is Channel 6, with the aural carrier at 87.7 MHz. That is .3
Mhz below the bottom edge of the 88 to 108 MHz FM Broadcast band.


Also,
these days, you could have digital TV signals starting immediately above
the FM (and still meeting the 'no interference' regulations for Air
Traffic Control radio. Do any cable systems still actually carry FM
radio?


Are you kidding? They were dropped as soon as the franchises stopped
asking for FM and wanted more video channels. They gained three midband
channels without rebuilding the system.


As well as protecting
against local oscillators, it also protects against incorrect loading
(ie if an output port is not correctly terminated in a 75 ohm load). It
should not matter (too much) if an output is left open circuit, short
circuited, has a length of cable connected to it but going nowhere, etc
etc.

Unterminated ports are not allowed in properly designed systems.
PERIOD.

They may be installed correctly terminated, but you can bet your bottom
dollar a lot won't stay that way!


Not if it's maintained by morons. But then, those systems were never
in spec.



I was the engineer at a CATV system with over 10,000
active drops. There are hundreds of myths and half truths about the
hardware used for CATV systems.

Was your statement above (about RLR) one of these? [Sorry. The Devil
made me say that! ;o))]

I find 2 ports with -6.5dB loss and one port with -3.5dB, which makes
more sense. (Actually, it should be -7.0dB loss).

While most 3-ways are typically 3.5/7/7, there are one or two around
with equal outputs, of appx 5.5dB (although, personally, I can't really
see much need for them).


You would, if the use of the 3.5/7/7 would require a second drop from
the line tap on the street.

When I said "much use", I meant "MUCH use". While a computerized CATV
system planner may flag up an out-of-spec condition, in practice, there
may be less than 1dB difference between a nominal 5.5 and 7dB.


So? If the franchise calls for all drops to be above 0 dB, one dB is
out of spec.


--
Offworld checks no longer accepted!

On Dec 9, 3:46*pm, "Michael A. Terrell"
wrote:
....snip...
* *A 0 dB or higer signal will overload the front end of a FM radio. O
dBM is 1000 microvolts @ 75 Ohms. FM radios are supposed to work at full
quieting 10 microvolts. *Some of the -20 dB taps were labeled as FM Taps
and were supposed to have a bandpass filter on the output port but none
of the ones I tested in the lab did.
....snip...

being a bit pedantic,
0 dBm in a 75 ohm system is 273,861 microvolts rms

On Dec 9, 3:46*pm, "Michael A. Terrell"
wrote:
....snip...
* *A 0 dB or higer signal will overload the front end of a FM radio. O
dBM is 1000 microvolts @ 75 Ohms. FM radios are supposed to work at full
quieting 10 microvolts. *Some of the -20 dB taps were labeled as FM Taps
and were supposed to have a bandpass filter on the output port but none
of the ones I tested in the lab did.
....snip...

being a bit pedantic,
0 dBm in a 75 ohm system is 273,861 microvolts rms

On Dec 9, 3:46*pm, "Michael A. Terrell"
wrote:
....snip...
* *A 0 dB or higer signal will overload the front end of a FM radio. O
dBM is 1000 microvolts @ 75 Ohms. FM radios are supposed to work at full
quieting 10 microvolts. *Some of the -20 dB taps were labeled as FM Taps
and were supposed to have a bandpass filter on the output port but none
of the ones I tested in the lab did.
....snip...

being a bit pedantic,
0 dBm in a 75 ohm system is 273,861 microvolts rms

Robert Macy wrote:

On Dec 9, 3:46 pm, "Michael A. Terrell"
wrote:
...snip...
A 0 dB or higer signal will overload the front end of a FM radio. O
dBM is 1000 microvolts @ 75 Ohms. FM radios are supposed to work at full
quieting 10 microvolts. Some of the -20 dB taps were labeled as FM Taps
and were supposed to have a bandpass filter on the output port but none
of the ones I tested in the lab did.
...snip...

being a bit pedantic,
0 dBm in a 75 ohm system is 273,861 microvolts rms


I meant 0 dBmv, which is used in TV Land.


--
Offworld checks no longer accepted!

On Dec 10, 8:56*am, "Michael A. Terrell"
wrote:
Robert Macy wrote:

On Dec 9, 3:46 pm, "Michael A. Terrell"
wrote:
...snip...
* *A 0 dB or higer signal will overload the front end of a FM radio. O
dBM is 1000 microvolts @ 75 Ohms. FM radios are supposed to work at full
quieting 10 microvolts. *Some of the -20 dB taps were labeled as FM Taps
and were supposed to have a bandpass filter on the output port but none
of the ones I tested in the lab did.
...snip...

being a bit pedantic,
0 dBm in a 75 ohm system is 273,861 microvolts rms

* *I meant 0 dBmv, which is used in TV Land.

--
Offworld checks no longer accepted!

Understood. Thanks.